Irrigation systems that deliver water, often containing plant nutrients, pesticides and/or medications, to plants via networks of irrigation pipes are very well known. Water from the pipes is delivered to the plants though an array of water outlet ports formed in the pipes and/or various types of emitters or drippers that are installed on or integrated inside the pipes. Typically, a network of irrigation pipes used to irrigate a field crop is laid down in a field in which the crop is grown at the beginning of the crop growing season and removed from the field at the end of the season. The same irrigation pipes are generally used repeatedly for a number of growing seasons until damage and wear renders the pipes inefficient for use at which time they are discarded.
Irrigation pipes are conventionally made from non-biodegradable petroleum based plastics such as polyethylene or polypropylene. As a result, conventional irrigation pipes that are discarded are generally not readily recycled into the environment and add to pollution stress of the environment. In addition, because petroleum is a non-renewable raw material, it is expected that raw material costs for producing irrigation pipes from petroleum-based plastics will increase.
U.S. Pat. No. 3,774,850 describes an irrigation “tube” that is formed from a “biodegradable, organic polymer composition which will decompose at the end of a growing season of a particular type of plant with which the tube is used.” The patent considers that “there are many biodegradable polymers and compositions from which the described irrigation pipes may be formed”. However, the patent notes only a composition “disclosed in the U.S. Pat. No. 3,590,528 entitled, “Decomposable Polybutene-1 Agricultural Mulch Film” issued to Thomas H. Shepard Jul. 6, 1971.” Nor does the patent describe how the composition is configured to “decompose at the end of a growing season of a particular type of plant with which the tube is used.” It is noted that European norm EN 13432 defines characteristics a material must have in order to be claimed as “compostable”. Polybutene-1 does not appear to have the characteristics.
On the other hand, the patent does indicate that, “It is also preferred that the tubes . . . be formed so that they are sufficiently thin as to be capable of being broken up easily at the end of the growing season utilizing conventional agricultural equipment such as is utilized to plow under grown plants or as to otherwise till or cultivate the soil. This feature of making these tubes so that they can be easily broken up in this manner is considered important in alleviating the necessity for recovery operations.” The breaking up forms pieces that are more readily biodegraded as the patent notes: “When a tube as herein described is formed out of a bio-degradable material the breaking up and plowing under of the tube is considered to facilitate bio-degration (sic) of the tube at the end of a growing season.”